Alarm devices for interconnected multi-device systems

Abstract

Alarm devices are provided with circuit means for permitting interconnection of the alarm devices into an alarm system in which each of the alarm devices continually senses for an adverse condition, such as smoke in a smoke detection alarm system, and in which all of the alarm devices signal an alarm in response to the sensing of an adverse condition. The interconnections for the alarm devices are such that the alarm devices not directly coupled to operative sources of electric power will, nevertheless, sense adverse conditions and signal alarms when any one of the alarm devices senses an adverse condition.

What is claimed as new and is desired to secure by Letters Patent of the United States is: 
     
       1. An alarm device adapted for use in a multidevice alarm system, said alarm device comprising: terminal means for connection to a source of electric power;   an alarm circuit coupled to said terminal means, said alarm circuit comprising normally conductive alarm means connected in series with normally non-conductive (OFF) switching means;   energy storage means coupled to said terminal means, said energy storage means connected in series with said alarm circuit and said energy storage means having sufficient electrical energy storage capacity to operate said alarm means for a discernable period of time;   control means coupled to said terminal means and said switching means for sensing an adverse condition and supplying an output signal to said switching means in response thereto, said switching means switching to a conductive state (ON) only while an output signal is supplied thereto; and   circuit means connected to said switching means for permitting the interconnection of said switching means in parallel with the switching means of one or more other alarm devices such that a source of electric power connected to the terminal means of at least one interconnected alarm device will charge the energy storage means of all of the interconnected alarm devices, whereby the alarm means of all of the interconnected alarm devices will operate in response to the sensing of an adverse condition by any one of the inter-connected alarm devices.   
     
     
       2. An alarm device as defined in claim 1 in which said energy storage means comprises a capacitor, said alarm device further comprising power supply means coupled between said terminal means and said alarm circuit, said energy storage means, and said control means for converting alternating current electric power to direct current electric power. 
     
     
       3. An alarm device as defined by claim 1 in which said control means comprises at least one detection element for detecting the presence of combustion and an electronic circuit for producing an output signal when combustion is detected, and in which said switching means comprises a semi-conductor switching element having a control input coupled to said electronic circuit for receiving output signals therefrom. 
     
     
       4. An alarm device as defined by claim 3 in which said semi-conductor switching element is a silicon-controlled rectifier (SCR). 
     
     
       5. An alarm device as defined by claim 4 in which said energy storage means comprises a capacitor, said alarm device further comprising power supply means coupled between said terminal means and said alarm circuit, said energy storage means, and said control means for converting alternating current electric power to direct current electric power. 
     
     
       6. An alarm device as defined by claim 1 in which said circuit means comprises a pair of output lines for interconnection to one or more other alarm devices, said circuit means further comprising a normally closed interlock switch connected in series with said switching means intermediate said output lines, whereby opening of said normally closed interlock switch will prevent operation of the alarm device. 
     
     
       7. An alarm system comprising: a plurality of alarm devices each comprising: terminal means for connection to a source of electric power;   an alarm circuit coupled to said terminal means, said alarm circuit comprising normally conductive alarm means connected in series with normally non-conductive (OFF) switching means;   energy storage means coupled to said terminal means, said energy storage means connected in series with said alarm circuit and said energy storage means having sufficient electrical energy storage capacity to operate said alarm means for a discernible period of time; and   control means coupled to said terminal means and said switching means for sensing an adverse condition and supplying an output signal to said switching means in response thereto, said switching means switching to a conductive state (ON) only while an output signal is supplied thereto; and     means interconnecting all of said switching means in parallel such that a source of electric power connected to the terminal means of at least one of said alarm devices will charge the energy storage means of all of said alarm devices;   whereby the alarm means of all of said alarm devices will operate in response to the sensing of an adverse condition by any one of said alarm devices.   
     
     
       8. An alarm system as defined by claim 7 in which the energy storage means of each of said alarm devices comprises a capacitor, each of said alarm devices further comprising power supply means coupled between said terminal means and said alarm circuit, said energy storage means, and said control means for converting alternating current electric power to direct current electric power. 
     
     
       9. An alarm system as defined by claim 8 in which the control means of each of said alarm devices comprises at least one detection element for detecting the presence of combustion and an electronic circuit for producing an output signal when combustion is detected, and in which said switching means comprises a silicon-controlled rectifier (SCR), having a control input coupled to said electronic circuit for receiving output signals therefrom.